In the past, somewhat complex hooks and couplings have been used to suspend cargo for the purpose of transporting it from one site to another and then remotely and/or automatically unloading such cargo. The cargo may be deposited on a platform, whether it be a ship-at-sea or a truck on land, by decoupling it at the desired site, preferrably with no personnel at the site to disengage the load.
Single-point operation has been preferred over multi-point (or multi-coupling) operation, particularly for externally-slung helicopter loads. However, two-point operation would provide greater load stability,--because of less twisting and swaying of the load. In manual decoupling of loads, it is obvious that more time would be consumed and required to disengage two coupling devices than one device, unless both devices were uncoupled simultaneously by a remote means. One also should bear in mind that each coupling device may have appreciable weight, another factor to consider when deciding how many couplings to use.
A coupling device should provide safety and economy in making such loadings and unloadings with ease in positioning and releasing the suspended load at the desired site.
The Boeing heavy lift helicopter (Vol. II s 301-10000-2 of Oct. 31, 1973, Contract DAAJ01-71-C-0840 (P40)), states that hook-up time at a prepared site is to be performed in no more than two (2) minutes. To meet this time requirement, a cable, separate from the hoist tension cables, attached directly to each coupling, deployed from a separately-powered cable reel, mounted adjacent to the main hoists, was recommended by Boeing-Vertol. The cable would carry conductors for mechanizing a remote mechanical hook release system, to run from the coupling at the load to the crew station within the aircraft.
The device suggested here would be simpler in construction than the Boeing hook mechanism. Also, the need for skilled personnel at the loading site to remove cargo could be unnecessary. Just any laborer could remove cargo, should ground personnel be required.